Maccabee has been an active ufologist since the late 1960s when he joined the National Investigations Committee on Aerial Phenomena (NICAP) and was active in research and investigation for NICAP until its demise in 1980. He became a member of the Mutual UFO Network (MUFON) in 1975 and was subsequently appointed to the position of state Director for Maryland, a position he still holds. In 1979 he was instrumental in establishing the Fund for UFO Research (FUFOR) and was the chairman for about 13 years. He presently serves on the National Board of the Fund.

His UFO research and investigations (which, he often stresses, are completely unrelated to his Navy work) have included the Kenneth Arnold sighting (June 24, 1947), the McMinnville, Oregon (Trent) photos of 1950, the Gemini 11 astronaut photos of September, 1966, the Tehran UFO incident of September 1976, the New Zealand sightings of December 1978, the Japan Airlines (JAL1628) sighting of November 1986, the numerous sightings of Gulf Breeze UFO incident, 1987–1988, the "red bubba" sightings, 1990-1992 (including his own sighting in September, 1991), the Mexico City video of August, 1997 (which he deemed a hoax),[6] the Phoenix lights sightings of March 13, 1997, and many others.[7][8][9]

He has also done historical research and was the first to obtain the secret "flying disc file" of the FBI (what he calls "the REAL X-Files"). In addition, he has collected documents from the CIA, the U.S. Air Force, the U.S. Army, and other government agencies.

Maccabee is the author or coauthor of about three dozen technical articles and more than a hundred UFO articles over the last 30 years, including many which appeared in the MUFON UFO Journal and MUFON Symposium proceedings. Among his papers was a reanalysis of the statistics and results of the famed Battelle Memorial InstituteProject Blue Book Special Report No. 14, a massive analysis of 3200 Air Force cases through the mid-1950s. (See Identified Flying Objects (IFOs)). Another was a reanalysis of the results of the Condon Committee UFO study from 1969. (Like many others, Maccabee concluded that Edward Condon lied about the results.)

In addition, he has also written or contributed to half a dozen books on the subject of UFOs and appeared on numerous radio and TV shows and documentaries (some given below) as an authority on the subject.

Maccabee is also an accomplished pianist who performed at the 1997 and 1999 MUFON symposia. He lives in Allen County, Ohio and married to Jan Maccabee.

"Prosaic Explanations, the Failure of UFO Skepticism," Infinite Energy Magazine, Issue #29, 2000; complete version in the Proceedings of the International MUFON Symposium, 2000; Updated version in UFO Magazine November and December, 2007